The physiological pharmacokinetic model for the body disposition of 2,5-HD has been formulated and verified for its basic elements. The blood, plasma, liver, kidney, muscle, fat, lung, skin and especially sciatic nerve, (lumbar) spinal cord, and some brain tissue levels can now be predicted for 14C radio-labeled 2,5-HD. Remaining questions are in two areas: 1) local uptake of 2,5-HD into nerves, and resulting possible inhibition of key enzymes; 2) lung uptake of the toxic agent and/or its precursors. The first is being approached with autoradiography and microdissection techniques, and should lead to better understanding of some origins of the neurological lesions. The second will focus on utilizing concepts from anesthesiology modeling in order to add the lung uptake process to the overall pharmacokinetic model.